Like in humans, the physiological systems of plants use hormones. Plant hormones govern their development, starting from the formation and maturation of the embryos, the germination of the seed, the seedling growth, and maturation and flowering. The end of a plant’s life is also orchestrated by hormones as a normal procedure. Besides, in their natural habitats, plants are exposed to fluctuations of temperature, light intensity, and water availability, which shape their basic abiotic environment. Their continuous contact and interaction with the living part of their habitats form their biotic environment, consisting of many types of organisms, like bacteria, fungi, viruses, insects and animals, including humans. Plants understand and “decide” how to react to all these interactions, regulating their cellular content, organs’ structure, and ultimately their development. While their development is a relatively anticipated and well-described biological procedure, their environmental responses are rather spontaneous, ad-hoc decisions.
From the moment of perception of an environmental stimulus, plants react at molecular and cellular level. Besides other biochemical compounds, plant hormones are the first, metabolizable effectors on plants’ own physiology, orchestrating their responses. Local hormone biosynthesis, or systematic transport or diffusion alters the overall hormonal homeostasis, signaling the metabolic, transcriptional, or molecular reform of the plant body to alleviate or tolerate stress. For this, the spatiotemporal distribution of hormones in plants is of paramount importance. The methods to determine it are based on biochemical analysis of plant parts, or enzymatic reactions happening within the plant tissues, producing color so we can visualize them. Those methods are destructive to plants’ tissues and do not allow continuous visualization. The less invasive and destructive method is the expression and visualization of fluorescent markers. However, this requires irradiation with strong ultraviolet light, to which long exposure destroys the tissues.
HorLumAS is a research-oriented project addressing this by implementing spontaneously emitted luminescence by plants. In nature, several species of fungi, marine animals, insects, and even some worms, emit luminescence. The biochemical pathway for the autonomous bioluminescence (ABL) of the fungus Neonothopanus nambi was described as a concerted action of 3 enzymes. First, using endogenous precursor molecules, two enzymes synthesize a high-energy biomolecule, termed Fungal Luciferin (FLin), which is oxidized by a specialized enzyme, termed Fungal Luciferase (FLase) with concurrent emission of green light. The idea behind HorLumAS is to create plants and cell suspensions engineered to emit ABL according to the spatiotemporal distribution of plant hormones. First we created transcriptional units for the FLin biosynthetic enzymes and transfer them into the plants, to synthesize FLin throughout their body and lifetime. Then a hormone-regulated transcriptional unit expresses FLase and makes the plant tissues emit ABL wherever and whenever a particular hormone appears.
The objectives of the project are to
- create ABL-emitting model plants of Arabidopsis thaliana and Nicotiana tabacum cell suspensions, Bright Yellow 2 (BY2) cells, and test whether ABL biochemistry affects them,
- standardize imaging methods with both scientific systems and commercial cameras, and script processing and quantification protocols for obtained images,
- create hormone-sensitive ABL reporter plants for auxins, cytokinins, abscisic acid, ethylene, gibberellins, brassinosteroids, salicylic acids, jasmonates, and strigolactones.
- investigate the spatiotemporal distribution of plant hormones when plants experience stressful conditions.
